Polarizing feed apparatus for biconical antennas

ABSTRACT

Apparatus is disclosed for feeding a single biconical antenna of the type having an upper and a lower cone which are connected to a coaxial feed line, the apices of said cones being in close proximity. The apparatus comprises means for vertically feeding said antenna, the vertical feed means being located at the apices of the cones. Means are also provided for horizontally feeding the antenna, the horizontal feed means being located in the vicinity of the apices of said cones. This combination of feed apparatuses permits the utilization of the vertical, horizontal, slant linear and circular polarization without the necessity of an external polarizer.

343*756a bR [451 Aug. 13, 1974 POLARIZING FEED APPARATUS FOR BICONICALANTENNAS [75] Inventor: Stephen E. Lipsky, East Hills, NY.

[73] Assignee: General Instrument Corporation,

Newark, NJ.

[22] Filed: Mar. 12, 1973 [21] Appl. No.: 340,322

[52] U.S. Cl 343/773, 343/726, 343/756 [51] Int. Cl.. H01q 13/00, l-l0lq19/00, H0lq 21/00 [58] Field of Search 343/773, 726, 756

[56] References Cited UNITED STATES PATENTS 2,532,428 12/1950 Smith343/756 OTHER PUBLlCATIONS Southworth, Principles and Applications ofWaveguide Transmission, Aug. l950, pp. 419-420 Primary Examiner-James W.Lawrence Assistant Examiner-T. N. Grigsby [57 ABSTRACT Apparatus isdisclosed for feeding a single biconical antenna of the type having anupper and a lower cone which are connected to a coaxial feed line, theapices of said cones being in close proximity. The apparatus comprisesmeans for vertically feeding said antenna, the vertical feed means beinglocated at the apices of the cones. Means are also provided forhorizontally feeding the antenna, the horizontal feed means beinglocated in the vicinity of the apices of said cones. This combination offeed apparatuses permits the utilization of the vertical, horizontal,slant linear and circular polarization without the necessity of anexternal polarizer.

12 Claims, 5 Drawing Figures PATENTEDM 13 m4 SHEET 10F 2 F/GZPATENTEDAus 13 1914 sum 80? 2 PROCESSING NETWORK POLARIZING FEEDAPPARATUS FOR BICONICAL ANTENNAS The present invention relates to feedapparatus for biconical antennas and more particularly to method andapparatus for feeding a biconical antenna which permits the reception ortransmission of waves of any polarization, including slant, linear orcircularly polarized waves, without the need for conventional polarizersnormally employed for this purpose.

The biconical antenna is capable of providing a uniform omniazimuthalpattern over a frequency range exceeding an octave. Because of thisfeature, biconical antennas have proved useful in a number ofapplications, particularly those having to do with reconnaissance.However, it was not previously known how to construct a biconicalantenna which could be utilized with polarizations of all orientationswithout physical reorientation of the antenna. Prior art attempts toovercome this problem have normally been accomplished through the use ofan external polarizer fitted about the antenna or within the throat ofthe bicone itself. Such polarizers were necessary because the feedapparatuses previously available for use with biconical antennas havebeen able'to produce only either vertical or horizontal polarization.Due to this deficiency, the encumberance and limitations inherent in theuse of external polarizers were deemed unavoidable.

Two principal types of polarizers are currently being used withbiconical antennas. Both of these types of polarizers consistof a seriesof concentric cylinders having parallel wires arranged on the surface ofeach cylinder. The angle which the wires make with one axis of thebicone increases for each successive cylinder. Normally, the wires areproduced by printed circuit techniques and are separated and supportedby a low loss rigid foam structure. The basic principle of operation forboth types of polarizers is identical. Either a vertical or horizontalfeed structure is used in the biconical antenna. For example, consider abiconical antenna which is vertically fed. Ideally, the polarizer willpermit vertically polarized waves to pass through the feed structureunhampered. Horizontally polarized waves will be redirected through thepolarizer and emerge as vertically polarized waves at the feed. In thisway either polarization is received by the vertical polarized feed as avertically polarized wave.

In the first type of polarizer, the printed wires are resonant at thefrequency of the signal. When a vertical feed structure is employed, ahorizontal wave is received by the first set of wires located on theoutermost cylinder. These wires are offset from the horizontal by asmall angle. The wires of this cylinder accept a component of thehorizontal field and reradiate it at the offset angle. The wires on thenext successive concentric cylinder are offset at a greater angle fromhorizontal, but are at a relatively small offset angle with respect tothe set of wires on the first concentric cylinder. The set of wires onthe second concentric cylinder accepts the wave reradiated from thefirst concentric cylinder and in turn reradiates this energy with thepolarization determined by its own offset angle. Each successive set ofwires on each successive concentric cylinder progressively shifts thepolarization until it is vertically polarized and can be accepted by thefeed. It can be seen from the resonant character of the wires used, thatthis type of polarizer is frequency sensitive.

The second type of polarizer is not as frequency sensitive as the onepreviously described. In this type of polarizer, the ends of the wiresare grounded at the top and bottom of the polarizer to form the boundaryof a twisted guide. Again using the vertical feed as an example, the setof wires on the first concentric cylinder will be offset from thevertical axis by a small angle (as opposed to the horizontal axis withthe resonant polarizers previously described). The offset angle of eachsuccessive set of wires on each successive concentric cylinder isincreased to form a twisted guide which will duct a horizontallypolarized wave received at the outside cylinder of the polarizer to thefeed as a vertically polarized wave.

Although the second type of polarizer is not as frequency sensitive asthe first, it is frequency limited and represents a significant designproblem if greater than octave frequency coverage is desired. Bothpolarizers normally represent a loss in antenna efficiency, an increasein antenna size and greater development and production costs. Thepresent invention relates to methods whereby the external polarizer canbe eliminated through a novel design of feed apparatus.

It is therefore a prime object of the present invention to provide afeed apparatus for a biconical antenna which will simultaneously acceptvertical and horizontal polarization without physical reorientation ofthe antenna and without the necessity of an external polarizer.

lt is a further object of the present invention to provide a feedapparatus for a biconical antenna which will accept slant linearpolarization as well as circular polarization without the necessity foran external polarizer.

In accordance with the present invention, apparatus is provided forfeeding a single biconical antenna of the type having an upper and lowercone which are connected to a coaxial feed line and in which the apicesof said cones are in close proximity. A means for vertically feeding theantenna is located at the apices of the cones. Means for horizontallyfeeding the antenna is additionally provided, the horizontal feed meansbeing located in the vicinity of the apices of the cones. Thecombination of a vertical feed apparatus and a horizontal feed apparatusin a single biconical antenna permits the generation and reception ofhorizontal, vertical, slant linear and circular polarizationssimultaneously in the same antenna structure without the necessity ofexternal polarizing mechanisms.

The results obtained through the use of the method and apparatusdisclosed herein are achieved through the use of separate vertical andhorizontal feed apparatuses used in combination. Three separate methodsof combining the vertical and horizontal feed apparatuses in a biconicalantenna are herein described for purposes of illustration. The first andthird embodiments of the present invention disclosed herein exemplifytwo parallel type combinations for the vertical and horizontal feedapparatus. The second embodiment exemplifies a form of seriescombination which can be used to achieve the desired results.

The drawings, which form a part of this application, illustrate severalpreferred embodiments of thepresent invention wherein like numerals areused to refer to like parts.

FlG. l is a plan viewof a typical biconical antenna with a vertical feedapparatus.

FIG. 2 is a plan view of a typical biconical antenna with a horizontalfeed apparatus.

FIG. 3 is a plan view of the first embodiment of the present inventionshowing a horizontal feedl loop connected in parallel with the verticalfeed apparatus.

FIG. 4 is a plan view of the second embodiment of the present inventionshowing a horizontal feed loop in series with the vertical feedapparatus in a biconical antenna.

FIG. 5 is a plan view of a third embodiment of the present inventionwherein two feed lines are utilized, one of which feeds the horizontalloop and the other which feeds the vertical feed apparatus in a parallelconfiguration.

FIG. 1 illustrates a vertical feed structure for a biconical antenna.The typical biconical antenna comprises two cones, a lower cone,designated as l, and an upper cone designated as 2. The apices of lowercone 1 and upper cone 2 are in close proximity in the throat area 3 ofthe biconical antenna. For purposes of better illustrating the feedstructures shown in these drawings, the throat portion 3 of each of thebiconical antennas which appear in the drawings has been slightlyextended. The biconical antenna in FIG. 1 is fed by a coaxial feed lineconsisting of an outer conductor 5 and an inner conductor 4. The outerconductor 5 is operably connected to the lower cone 1 and the innerconductor 4 extends through the throat portion 3 and is operablyconnected to the upper cone 2. This is the typical configuration for avertically fed biconical antenna.

The field of the TEM mode in the coaxial feed lines extends radiallyfrom the outer conductor to the inner conductor. As the wave propogatesbeyond the coaxial feed to the throat and then to the cones of theantenna, it emerges as a vertically polarized wave with the fieldextending from the lower cone to the upper cone. When used in this way,the bicones can be viewed as extensions of the coaxial feed line, theupper and lower cones serving as matching extensions to free space forthe inner and outer conductors respectively.

In FIG. 2 apparatus for generating a horizontal polarization in abiconical antenna is shown. The means for generating horizontalpolarization in the antenna is preferably in the form of a horizontalloop 6 located in the throat portion 3 of the biconical antenna. Thishorizontal loop 6 is actively fed by the coaxial feed line, oneconductor of which is operably connected to each end of the loop 6.

FIG. 3 illustrates the combination of a vertical and horizontalpolarization feed apparatus connected in a parallel combination in asingle biconical antenna. In this embodiment the inner coaxial conductor4 of the feed line is connected to supply the horizontal loop 6 as wellas the upper cone 3. The horizontal loop 6 is connected between theinner conductor 4 and the lower cone 1. The design of the vertical andhorizontal feeds and the matching sections are such that energy andphase division between the vertical and horizontal modes of energy inthe bicone can be controlled. If, at a particular frequency, a 90 phasedifference between equal horizontal and vertical waves exists in thebicone, circular polarization will result. The feed networks aredesigned to achieve this difference by their design and by the divisionof energy in each feed.

FIG. 4 illustrates a second embodiment of the present invention whereinthe vertical and horizontal feed apparatus are connected in series. Thehorizontal loop 6 is preferably connected in series with the innerconductor 4 of the coaxial feed line which feeds the upper cone 3. Theloop 6, illustrated in this embodiment, can be in the form of a spiralor a horizontal loop similar to that shown in FIG. 3. The energydivision between the vertical and horizontal mode is determined by theeffective radiation resistance of the loop 6 and the vertical feed tothe bicone. For equal power division, the r'a' diation resistances ofeach mode should be equal. These resistances are controlled, in part, bythe design of the antenna and feed elements and by the matchingimpedance of the loop 6. The actual design parameters will be chosen tooptimize the polarization effects desired. The same factors, includingthe phase shift and wave propagation, which affect the design of theparallel mode, shown in FIG. 3 and described above, would affect thedesign of the series mode configuration shown in FIG. 4.

FIG. 5 illustrates a third embodiment of the present invention. In thisembodiment two separate coaxial feed lines are utilized to feed thevertical and horizontal feed apparatuses, respectively. A power divider9 is used to divide the input power between the two coaxial feed lines,generally designated as A and B, respectively. Feed line A consists ofan inner conductor 7 and outer conductor 8, each of which is connectedto a different end of horizontal loop 6 located in the throat portion 3of the bicone. The second output of power divider 9 is fed to aprocessing network 10, the output of which feeds the second coaxial feedline B. Coaxial feed line B is comprised of an inner conductor 4 and anouter conductor 5. The outer conductor 5 is operably connected to thelower cone 1 and the inner connector 4 is operably connected to theupper cone 3 thus forming the vertical polarization feed apparatus. Theprocessing network 10 can be utilized to supply several functions,including phase and amplitude variation with frequency. This type ofnetwork need not be restricted to only one feed line but may be placedat either or both lines, as necessary. Similarly, the power divider 9need not be restricted to equal power division.

The external circuitry shown in FIG. 5 as a power divider 9 and aprocessing network 10 can provide great flexibility in the performancewhich can be obtained from a biconical antenna. A lower radiationefficiency or an undesired phase shift from either feed apparatus can becompensated for in this circuitry. Through proper shaping of thecharacteristics of the external circuitry, compensation for feedstructure deficiencies over a range of frequencies can be made therebyincreasing the operationg bandwidth of the bicone for combined feedstructure operation. In addition, the external circuitry is not limitedto operating performance enhancement. For special applications, it maybe desirable to receive only one polarization over a certain band. Thisis accomplished by placing two bandstop filters between quadraturehybrids in the feed line associated with the particular polarization.Out-of-band frequencies are passed while in-band frequencies arereflected to a load.

Even more sophisticated processing is possible with this arrangement.The characteristics of the external circuitry can be made time variableas well as frequency variable. Devices such as pin diodes and varactorscan be employed to vary the characteristics as desired. The antenna canbe adjusted for vertical, slant or right or left hand polarization oncommand. This facility is useful in identifying the polarization ofreceived signals and can also be used in coding a transmitted signal.This flexibility can be achieved almost instantaneously. It would bevirtually impossible to obtain this performance with fixed polarizers.

Further, the separate feed outputs are not restricted to being combinedin a power divider 9, but are capable of being used separately or beingpartially coupled. The two feed lines in FIG. 5 ideally represent twoseparate antennas, one vertically polarized and the other horizontallypolarized. Each can be directed to separate receivers or transmitters orother processing circuitry. The dual use of a single antenna optimizesthe use of available antenna area, an important factor in airborne andmilitary applications.

The components described as being contained in the external processingcircuitry can be contained within the bicone antenna. Theinterconnecting configuration used to connect the feed structures canperform matching and amplitude or phase shaping functions over afrequency range. The application of microcircuitry permits the locationof pinand varactor diodes as well as small filter networks within thebicone throat area when necessary.

In many practical cases the complexity and interaction of the feedstructure and the bicone causes the design approach to include a certaindegree of experimental verification. A myriad of structural variationson the basic concept of the present invention can thus be generated.While a limited number of embodiments have been disclosed herein forpurposes of illustration, it will be apparent that many variations canbe made therein, all without departing from the spirit of the inventionas defined in the appended claims.

I claim:

1. Apparatus for actively feeding a single biconical antenna of the typehaving an upper and a lower cone, the apices of which are in closeproximity comprising vertical feed means for exciting the antenna in afirst mode and horizontal feed means for exciting the antenna in asecond mode, said vertical feed means and said horizontal feed meanseach being situated in the vicinity of the apices of said cones, meansfor transmitting signals to and from said vertical feed means and saidhorizontal feed means respectively, said first and second modesinteracting to permit the transduction of polarized waves ofsubstantially all orientations by said antenna.

2. The apparatus according to claim 1 wherein said horizontal feed meanscomprises an actively fed horizontal loop.

3. The apparatus according to claim 1 wherein said signal transmissionmeans comprises a coaxial transmission line, said line being operablyconnected to each of said feed means.

4. The apparatus according to claim 3 wherein said line has an innerconductor operably connected to one of said cones and an outer conductoroperably connected to the other of said cones to form said vertical feedmeans.

5. The apparatus according to claim 4 wherein said horizontal feedapparatus is operably connected between said cones.

6. The apparatus according to claim 4 wherein said horizontal feedapparatus is operably connected between one of said cones and theconductor operably connected to said one cone.

7. The apparatus according to claim 1 wherein said signal transmissionmeans comprises a first and a second coaxial transmission line, saidfirst line operably connected to said vertical feed means for activelyfeeding same and said second line operably connected to said horizontalfeed means for actively feeding same.

8. The apparatus according to claim 7 wheri n said horizontal feed meanscomprises a horizontal loop.

9. The apparatus according to claim 8 wherein said loop has a first anda second end, said first end being operably connected to the innerconductor of said second line and said second end being operablyconnected to the outer conductor of said second line.

10. The apparatus according to claim 8 wherein said first transmissionline has an inner conductor connected to one of said cones and an outerconductor connected to the other of said cones to form said verticalfeed means.

11. Apparatus for feeding a biconical antenna of the type having anupper and a lower cone the apices of which are in close proximitycomprising means for vertically feeding said antenna, a coaxialtransmission line and a horizontal loop located in the vicinity of theapices of said antenna, said loop having a first and a second end, saidfirst end operably connected to said inner conductor and said second endoperably connected to said outer conductor such that said loop isactively fed by said line.

12. A method for feeding a single biconical antenna such that saidantenna can be utilized with polarization of any orientation, saidantenna being formed of an upper and a lower cone the apices of whichare in close proximity, having a horizontal loop situated in thevicinity of the apices and being fed by a coaxial transmission linecomprising the steps of:

vertically feeding said antenna through an operable connection betweenthe inner conductor of said transmission line and one of said cones andbetween the outer conductor of said transmission line and the other ofsaid cones and horizontally feeding said antenna through an operableconnection between one end of said loop and said inner conductor of saidtransmission line and between the other end of said loop and said outerconductor of said transmission line.

1. Apparatus for actively feeding a single biconical antenna of the typehaving an upper and a lower cone, the apices of which are in closeproximity comprising vertical feed means for exciting the antenna in afirst mode and horizontal feed means for exciting the antenna in asecond mode, said vertical feed means and said horizontal feed meanseach being situated in the vicinity of the apices of said cones, meansfor transmitting signals to and from said vertical feed means and saidhorizontal feed means respectively, said first and second modesinteracting to permit the transduction of polarized waves ofsubstantially all orientations by said antenna.
 2. The apparatusaccording to claim 1 wherein said horizontal feed means comprises anactively fed horizontal loop.
 3. The apparatus according to claim 1wherein said signal transmission means comprises a coaxial transmissionline, said line being operably connected to each of said feed means. 4.The apparatus according to claim 3 wherein said line has an innerconductor operably connected to one of said cones and an outer conductoroperably connected to the other of said cones to form said vertical feedmeans.
 5. The apparatus according to claim 4 wherein said horizontalfeed apparatus is operably connected between said cones.
 6. Theapparatus according to claim 4 wherein said horizontal feed apparatus isoperably connected between one of said cones and the conductor operablyconnected to said one cone.
 7. The apparatus according to claim 1wherein said signal transmission means comprises a first and a secondcoaxial transmission line, said first line operably connected to saidvertical feed means for actively feeding same and said second lineoperably connected to said horizontal feed means for actively feedingsame.
 8. The apparatus according to claim 7 wherein said horizontal feedmeans comprises a horizontal loop.
 9. The apparatus according to claim 8wherein said loop has a first and a second end, said first end beingoperably connected to the inner conductor of said second line and saidsecond end being operably connected to the outer conductor of saidsecond line.
 10. The apparatus according to claim 8 wherein said firsttransmission line has an inner conductor connected to one of said conesand an outer conductor connected to the other of said cones to form saidvertical feed means.
 11. Apparatus for feeding a biconical antenna ofthe type having an upper and a lower cone the apices of which are inclose proximity comprising means for vertically feeding said antenna, acoaxial transmission line and a horizontal loop located in the vicinityof the apices of said antenna, said loop having a first and a secondend, said first end operably connected to said inner conductor and saidsecond end operably connected to said outer conductor such that saidloop is actively fed by said line.
 12. A method for feeding a singlebiconical antenna such that said antenna can be utilized withpolarization of any orientation, said antenna being formed of an upperand a Lower cone the apices of which are in close proximity, having ahorizontal loop situated in the vicinity of the apices and being fed bya coaxial transmission line comprising the steps of: vertically feedingsaid antenna through an operable connection between the inner conductorof said transmission line and one of said cones and between the outerconductor of said transmission line and the other of said cones andhorizontally feeding said antenna through an operable connection betweenone end of said loop and said inner conductor of said transmission lineand between the other end of said loop and said outer conductor of saidtransmission line.